Merge branch 'pci/aspm'

  - Use Latency Tolerance Reporting if already enabled by platform (Bjorn
    Helgaas)

  - Save/restore LTR info for suspend/resume (Bjorn Helgaas)

* pci/aspm:
  PCI/ASPM: Save LTR Capability for suspend/resume
  PCI/ASPM: Use LTR if already enabled by platform

2 files changed, 74 insertions, 15 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index c9d8e3c837de..13d65991c77b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1233,7 +1233,6 @@ static void pci_restore_pcie_state(struct pci_dev *dev)
 	pcie_capability_write_word(dev, PCI_EXP_SLTCTL2, cap[i++]);
 }
 
-
 static int pci_save_pcix_state(struct pci_dev *dev)
 {
 	int pos;
@@ -1270,6 +1269,45 @@ static void pci_restore_pcix_state(struct pci_dev *dev)
 	pci_write_config_word(dev, pos + PCI_X_CMD, cap[i++]);
 }
 
+static void pci_save_ltr_state(struct pci_dev *dev)
+{
+	int ltr;
+	struct pci_cap_saved_state *save_state;
+	u16 *cap;
+
+	if (!pci_is_pcie(dev))
+		return;
+
+	ltr = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR);
+	if (!ltr)
+		return;
+
+	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_LTR);
+	if (!save_state) {
+		pci_err(dev, "no suspend buffer for LTR; ASPM issues possible after resume\n");
+		return;
+	}
+
+	cap = (u16 *)&save_state->cap.data[0];
+	pci_read_config_word(dev, ltr + PCI_LTR_MAX_SNOOP_LAT, cap++);
+	pci_read_config_word(dev, ltr + PCI_LTR_MAX_NOSNOOP_LAT, cap++);
+}
+
+static void pci_restore_ltr_state(struct pci_dev *dev)
+{
+	struct pci_cap_saved_state *save_state;
+	int ltr;
+	u16 *cap;
+
+	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_LTR);
+	ltr = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR);
+	if (!save_state || !ltr)
+		return;
+
+	cap = (u16 *)&save_state->cap.data[0];
+	pci_write_config_word(dev, ltr + PCI_LTR_MAX_SNOOP_LAT, *cap++);
+	pci_write_config_word(dev, ltr + PCI_LTR_MAX_NOSNOOP_LAT, *cap++);
+}
 
 /**
  * pci_save_state - save the PCI configuration space of a device before suspending
@@ -1291,6 +1329,7 @@ int pci_save_state(struct pci_dev *dev)
 	if (i != 0)
 		return i;
 
+	pci_save_ltr_state(dev);
 	pci_save_dpc_state(dev);
 	return pci_save_vc_state(dev);
 }
@@ -1390,7 +1429,12 @@ void pci_restore_state(struct pci_dev *dev)
 	if (!dev->state_saved)
 		return;
 
-	/* PCI Express register must be restored first */
+	/*
+	 * Restore max latencies (in the LTR capability) before enabling
+	 * LTR itself (in the PCIe capability).
+	 */
+	pci_restore_ltr_state(dev);
+
 	pci_restore_pcie_state(dev);
 	pci_restore_pasid_state(dev);
 	pci_restore_pri_state(dev);
@@ -2998,6 +3042,11 @@ void pci_allocate_cap_save_buffers(struct pci_dev *dev)
 	if (error)
 		pci_err(dev, "unable to preallocate PCI-X save buffer\n");
 
+	error = pci_add_ext_cap_save_buffer(dev, PCI_EXT_CAP_ID_LTR,
+					    2 * sizeof(u16));
+	if (error)
+		pci_err(dev, "unable to allocate suspend buffer for LTR\n");
+
 	pci_allocate_vc_save_buffers(dev);
 }
 
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 43e6583417ce..1078195f244a 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2069,11 +2069,8 @@ static void pci_configure_ltr(struct pci_dev *dev)
 {
 #ifdef CONFIG_PCIEASPM
 	struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
-	u32 cap;
 	struct pci_dev *bridge;
-
-	if (!host->native_ltr)
-		return;
+	u32 cap, ctl;
 
 	if (!pci_is_pcie(dev))
 		return;
@@ -2082,22 +2079,35 @@ static void pci_configure_ltr(struct pci_dev *dev)
 	if (!(cap & PCI_EXP_DEVCAP2_LTR))
 		return;
 
-	/*
-	 * Software must not enable LTR in an Endpoint unless the Root
-	 * Complex and all intermediate Switches indicate support for LTR.
-	 * PCIe r3.1, sec 6.18.
-	 */
-	if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
-		dev->ltr_path = 1;
-	else {
+	pcie_capability_read_dword(dev, PCI_EXP_DEVCTL2, &ctl);
+	if (ctl & PCI_EXP_DEVCTL2_LTR_EN) {
+		if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT) {
+			dev->ltr_path = 1;
+			return;
+		}
+
 		bridge = pci_upstream_bridge(dev);
 		if (bridge && bridge->ltr_path)
 			dev->ltr_path = 1;
+
+		return;
 	}
 
-	if (dev->ltr_path)
+	if (!host->native_ltr)
+		return;
+
+	/*
+	 * Software must not enable LTR in an Endpoint unless the Root
+	 * Complex and all intermediate Switches indicate support for LTR.
+	 * PCIe r4.0, sec 6.18.
+	 */
+	if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
+	    ((bridge = pci_upstream_bridge(dev)) &&
+	      bridge->ltr_path)) {
 		pcie_capability_set_word(dev, PCI_EXP_DEVCTL2,
 					 PCI_EXP_DEVCTL2_LTR_EN);
+		dev->ltr_path = 1;
+	}
 #endif
 }